1. Field of the Invention
The present invention relates to spinal interbody devices for implantation between a pair of adjacent vertebrae in order to provide distraction and support to the adjacent vertebrae and/or promote bone fusion between the adjacent vertebrae.
2. Background Information
The disc between vertebrae of a human spine is sometimes damaged due to disease or injury, or may simply deteriorate due to age, disease, injury or congenital defect. With others, the vertebrae may become compressed or otherwise damaged. In these and other cases the vertebrae can become too closely spaced anteriorly which causes an undesired abnormal curvature of the spine with respect to lordosis or kyphosis.
Because of this, surgery may be utilized to place one or more devices between adjacent vertebrae in order to provide proper spacing of the adjacent vertebrae. Such devices may also be used to promote fusion between the vertebrae. When a device of this type is utilized for the purpose of promoting fusion, it is often termed an intervertebral or interbody fusion cage. When so utilized, bone or bone fusion material is often placed about or in the interbody cage in order to promote growth of the bone between the adjacent vertebrae.
One or more interbody fusion cages may be used. When multiple interbody fusion cages are used, bone fusion material may be packed between the interbody fusion cages that are then placed close to one another to promote bone growth and thus fusion.
It is desirable for the interbody fusion cage to engage as much surface of the bone as possible in order to provide proper support to the bone and thereby reduce the likelihood of subsidence of the device into the bone resulting from contact pressure of the interbody fusion cage against bone surfaces. Subsidence can occur since part of the bone is somewhat spongy in nature, especially near the center of the vertebra. In summation, the structure of interbody devices functions to support the two adjacent vertebral surfaces and to promote fusion of the adjacent vertebrae when packed with bone fusion material.
Current intervertebral devices are essentially static in configuration. An exception to this is with regard to height of the intervertebral device wherein it is known to have height adjustable intervertebral devices. However, because factors such as vertebral damage and/or individual anatomy can limit or dictate what type, size and or configuration of intervertebral device can be used with respect to the contact area or placement of the intervertebral device relative to adjacent vertebrae, it would be desirable to have an intervertebral device whose shape can be varied to accommodate such unpredictability.